I'm trying to add a field to an existing Sublist (not custom) but can't seem to figure this out. I've attached a photo for reference. This is for the customer record. I'm able to create a custom sublist by sourcing it from a Saved Search and I was able to make a custom field. But I can't seem to move the field or Custom sublist to this Contact sublist. Any advice?

If the sublist list is a standard record and you have added the field to the standard record, you probably just need to click that button that says "customize view" and add the field you are interested in. I'm not sure what the red box is you're highlighting as that is the area for filters. I don't tend to work in the UI or customise it but you may be able to add filters too via that view.

Thank you so much. That actually does help me. I was confusing myself with the filters. It makes sense now. Thank you ☺️